Whole blood contains red blood cells, white blood cells, platelets, clotting factors, and plasma. Aberrant levels of cellular and non-cellular components of blood can be used to detect or diagnose diseases. While some clinical tests are performed using whole blood, many blood tests use blood serum or plasma. Blood serum or plasma is typically obtained by centrifugation of blood. Serum is obtained by centrifuging whole blood following clotting, while plasma is obtained by centrifuging whole blood containing added anticoagulants.
The separation of serum or plasma from whole blood using centrifugation increases the turnaround time and requires the use of an electrical device. To perform diagnostic tests in point-of-care facilities or in underserved or budget-limited regions where electricity is unavailable or not easily accessible or centrifuge is unavailable or unaffordable, obtaining blood serum or plasma samples without the use of centrifuge or other electricity-powered devices is critical for providing healthcare.
Several centrifuge-free blood component separation devices are available. SeraSTAT® Rapid Blood Cell Separator (Akers Biosciences, Inc. West Deptford, N.J.) and HemaSpot™-SE Blood Separation Device (Spot On Sciences, Inc. Austin, Tex.) are two examples. SeraSTAT® rapid blood cell separator requires the use of blood component-specific agents in the filtration membrane. A blood sample enters from one side of the membrane and, after passing through the membrane, the cell-free blood components are collected at the opposite side of the membrane. The blood flows under an applied pressure, not under gravity.
HemaSpot™-SE blood separation device separates soluble components in the blood from blood cells and platelets based on their size-dependent flow speed through a horizontal, spiral-shaped flow channel. Liu et al. reported a small sized filtration device for plasma blood sample collection via a size-exclusion membrane. This device contains a two-chamber container separated by a size exclusion membrane. Blood sample is injected into one chamber and plasma is collected from another chamber after diffusing through the size exclusion membrane. Vemulapati et al. designed a device for plasma collection using functionalized magnetic beads to capture red blood cells and separate the red blood cells from the rest of the blood components. The U.S. Pat. No. 7,927,810 discloses a device for separation of plasma or serum from the blood cells using a filtration membrane having a certain porosity. Such device allows whole blood to pass through the membrane. By applying pressure from the top end of the device, blood plasma or serum is collected from the bottom of the container after flowing through the membrane.